Monday, January 30, 2017

Today
I decided to make a post on a very important topic, oxidative stress. This
subject is often referred to in biochemistry classes (and not only!), but it is
not always clear to the speaker or to the audience, what it actually
represents.Nevertheless,
the idea is simple to understand ... As I say many times in my classes, we have
a bad habit, which kills us slowly, without exception: we spend our lives breathing
oxygen! And
this molecule, so important for our biochemistry, in particular for aerobic
metabolism, is what kills us slowly, and makes us grow old. And
do not hesitate, if we do not die of an accident, or of some illness, we will
die because we have been breathing O2 during our life! :)So,
what does oxygen contain that makes it so dangerous? Basically
nothing, that is, the molecule itself is harmless to our molecules/cells. The
problem is in its susceptibility to suffer partial reductions, that is, to
capture electrons. In
fact, we are continually forming the so-called reactive oxygen species, which
are essentially 3: the hydroxyl radical (free radical), the superoxide anion
(free radical) and hydrogen peroxide. Of
these 3, the first two are more aggressive because they are free radicals. Free
radicals are molecules that have an unpaired electron (which is why they are
represented with a black speckle, which is that unpaired electron).

The
electrons have a serious problem, they do not like to walk alone, so they will
look for "companionship" in the first molecule that appears ahead, be
it a lipid, a protein or a nucleic acid. That
is, reactive oxygen species are highly reactive molecules, they are powerful
oxidizing agents, which will react with our biomolecules, removing an electron
and altering/destroying them. And
the problem is that although the free radical ceases to be when it picks up an
electron, the molecule with which it reacts becomes a free radical, giving rise
to a destructive chain process.To
counteract this, our cells have several defenses, called antioxidants. Therefore,
oxidative stress arises when we have an imbalance between the pro-oxidants
(reactive oxygen species and reactions that produce them) and the antioxidants
(processes that prevent the formation and/or action of the pro-oxidants),
favoring the
first, or disfavoring the seconds.